1. Field of the Invention
The present invention relates to a data processing method and a data processing device involving AD (analog-digital) conversion, a solid-state imaging device, which is an example of a semiconductor device for detecting a physical quantity distribution employing a mechanism of the AD conversion, an imaging apparatus, and an electronic device. More specifically, the present invention relates to a digital signal processing technique suitably used for a semiconductor device for detecting a physical quantity distribution and other electronic devices such as a solid-state imaging device that is formed by arraying plural unit components, which have sensitivity to electromagnetic waves inputted from the outside such as light and radiations, and can arbitrarily select, using address control, a physical quantity distribution converted into an electric signal by the unit components and read out the physical quantity distribution as the electric signal. More particularly, the present invention relates to a technique for acquiring digital data subjected to an arithmetic operation in treating plural kinds of processing object signals.
2. Description of the Related Art
In recent years, as examples of a solid-state imaging device, image sensors of a MOS (Metal Oxide Semiconductor) type and a CMOS (Complementary Metal-Oxide Semiconductor) type that can overcome various problems of a CCD (Charge Coupled Device) image sensor attract attention.
For example, the CMOS image sensor has, for each of pixels, an amplifier including a floating diffusion amplifier. In reading out a pixel signal, as an example of address control, a system of a so-called column parallel output type or column type is often used. This is a system for selecting one row in a pixel array section, simultaneously accessing pixels for the one row, and reading out pixel signals from the pixel array section in row units, i.e., all the pixels for the one row simultaneously and in parallel.
In the solid state imaging device, a system for converting an analog pixel signal read out from the pixel array section into digital data with an analog digital converter (an AD converter) and, then, outputting the digital data to the outside may be adopted.
The same applies to the image sensor of the column parallel output type. Various signal output circuits have been devised as a signal output circuit for the image sensor. As an example of a most advanced form of the image sensor, an image sensor of an AD conversion system that includes an AD converter for each of columns and extracts a pixel signal to the outside as digital data has been proposed (see, for example, JP-A-2005-323331).
As the AD conversion system, various systems have been devised from the viewpoints of a circuit size, processing speed (an increase in speed), resolution, and the like. As an example, there is an AD conversion system of a so-called slope integration type or ramp signal comparison type (in this specification, herein after referred to as reference signal comparison type). This is a system for comparing an analog unit signal and a so-called ramp-shaped reference signal (a ramp wave), a gradual value of which changes, for converting the unit signal into digital data, performing count processing in parallel with this comparison processing, and acquiring digital data of the unit signal on the basis of a count value at a point when the comparison processing is completed. JP-A-2005-323331 also discloses an example of an image sensor adopting the AD conversion system of the reference signal comparison type. By combining the AD conversion system of the reference signal comparison type and the column parallel output type, analog outputs from pixels can be AD-converted in column parallel in a low frequency band. Therefore, it can be said that the AD conversion system is suitable for an image sensor that realizes both a high image quality and high speed.
In the pixel signal, more specifically, a difference between a pixel signal level at the time of pixel reset and a pixel signal level at the time when a signal charge is read out is a true signal component. Therefore, even when the AD conversion system of the reference signal comparison type and the column parallel output type are combined to simultaneously convert all pixels in one row into digital data, a mechanism that takes into account the fact that difference processing is necessary is adopted. For example, JP-A-2005-323331 adopts a mechanism for automatically acquiring an AD conversion result of a true signal component, that is, a mechanism for performing a difference processing function simultaneously with the AD conversion, as a final AD conversion output value by making it possible to switch an up-count mode and a down-count mode and using different count modes in AD conversion at a pixel signal level at the time of pixel reset and in AD conversion at a pixel signal level at the time when a signal charge is read out.